The cladding system on the outside of Grenfell Tower was so conducive to the spread of fire it did not support the "stay-put" policy normally in place for a building of its type, a report has found.

The stay-put strategy pursued by the fire service on June 14 last year had "effectively failed" barely half an hour after the fire started, at 1.26am, Dr Barbara Lane wrote. 71 people died in the tragedy.

The kitchen from flat 16 at Grenfell Tower is seen in this undated handout image, presented as part of Professor Niamh Nic Daeid’s report to the Grenfell Tower Inquiry in London. Photo: Reuters

She also claimed that the key players involved in the 2016 refurbishment had not ascertained how the new cladding system would behave in a fire.

Fire safety engineer Dr Lane made the remarks in an expert report commissioned by the Grenfell Tower inquiry on the fire protection measures within the 25-storey building.

Tests showed the materials forming the cladding system, individually and together, did not comply "with the recommended fire performance" set out in guidance for a building of that height, the report said.

She wrote: "Additionally, I conclude that the entire system could not adequately resist the spread of fire over the walls having regard to height, use and position of the building.

"Specifically, the assembly failed adequately to resist the spread of fire to an extent that supported the required 'stay-put' strategy for this high-rise residential building.

"There were multiple catastrophic fire-spread routes created by the construction form and construction detailing."

The windows lacked fire resisting cavity barriers and were surrounded by combustible material, meaning there was a "disproportionately high probability" of fire spreading to the cladding, she added.

Dr Lane wrote: "I have found no evidence yet that any member of the design team or the construction ascertained the fire performance of the rainscreen cladding system materials, nor understood how the assembly performed in fire.

"I have found no evidence that Building Control were either informed or understood how the assembly would perform in a fire."

Neither the Tenant Management Organisation nor London Fire Brigade recorded how the cladding would respond to a fire in their risk assessments, she said.

Poorly performing fire doors "contributed significantly to the spread of smoke and fire to the lobbies," Dr Lane found.

She wrote in her report that this failure "would have materially affected the ability or willingness of occupants to escape independently through this space to the stair".

It would have also hindered the ability of firefighters to rescue many people on the tower's upper floors.

In 2011, the Tenant Management Organisation - which ran the building - replaced 106 flat entrance fire doors. None of the doors on any of the 120 flats - including the 14 not replaced - were compliant with the fire test evidence relied upon at the time of installation, Dr Lane found.

These shortcomings would have had a number of consequences, including failure to prevent the spread of smoke and flame by leakage through gaps between the door leaf and door frame.

Escape

Another failure of an "unknown number of doors" to self-close after an occupant escaped would have allowed "immediate" spread of fire and smoke.

The lobbies could therefore not be used as a "safe air environment" by the fire service bridgehead, forcing it to remain below level 4 until 7.30am.

"This greatly reduced the time available using breathing apparatus, and so the time available for rescue on the upper floors, and particularly above level 15," she said.

Firefighters may have contributed to the spread of fire and smoke into the stairwell by leaving doors ajar as they fought the blaze, Dr Lane found.

She wrote: "I have identified the fact that the firefighting operations in response to the multi-storey fire may have contributed to the failure of the stair fire doors to prevent fire and smoke spread.

"Current evidence indicates some of the stair doors were ajar as firefighting hoses were running from the stair into the lobby.

"However, I cannot yet conclude whether this made a significant contribution."

In one case, a fire door to the stairwell was held open by a body, the report said.

The automatic air ventilation system in the building was not "in accordance with current statutory guidance" and there was evidence it did not operate as intended, Dr Lane wrote.

The lifts in the building also failed to perform effectively in the fire, hindering firefighter equipment transport and creating an "unnecessary risk" to residents who could not use it to escape.

The tower also used a "dry fire main" - meaning the fire service had to pump it with its own water - that was "non-compliant with the design guidance in force at the time of the original construction and is also non-compliant with current standards".

This stopped firefighters getting water to the upper floors as effectively as a wet main, which provides more pressure by being already charged with a pump connected when the service arrives.

Four further expert reports have been released as the first day of evidence got under way.

In his opening remarks, Richard Millett QC, counsel to the inquiry, said: "The fundamental question which lies at the heart of our work is how, in London in 2017, a domestic fire developed so quickly and so catastrophically that an entire high rise block was engulfed, and how it was that 71 people lost their lives in a matter of hours."